//跨域请求
function cross(app){
    //设置跨域
app.use('*', function(request, response, next) {
  
    response.header('Access-Control-Allow-Origin', '*')
    //允许所有类型的请求头
    response.header('Access-Control-Allow-Headers', '*')
    //对请求和响应进行放行
    next()
  })
}
exports.cross = cross